A surgical microscope of the kind referred to above is known from U.S. Pat. No. 6,004,314. This surgical microscope includes an OCT-system which generates a scanning beam of short coherent laser radiation. The OCT-system includes an analyzer unit for evaluating interference signals. The OCT-system further includes a device having two scan mirrors for scanning the OCT-scanning beam. These scan mirrors can be displaced about two axes of movement. The OCT-scanning beam in the surgical microscope is coupled via a divider mirror into the illuminating beam path of the surgical microscope. The OCT-scanning beam is deflected with the illuminating beam through the microscope main objective to the object region.
Via optical coherence tomography, an OCT-system makes possible the non-invasive display and measurement of structures within a tissue. As an optical image producing method, the optical coherence tomography especially generates section and volume images of biological tissue with a micrometer resolution. A corresponding OCT-system includes a source for time-dependent incoherent and spatially coherent light having a specific coherence length which is guided to a specimen beam path and a reference beam path. The specimen beam path is directed to the tissue to be examined. Laser radiation, which is backscattered into the specimen beam path because of scatter centers in the tissue, superposes the OCT-system with laser radiation from the reference beam path. An interference signal results because of the superposition. The positions of the scattering centers for the laser radiation in the examined tissue are determined from this interference signal.
For OCT-systems, the building principles of the “time-domain OCT” and of the “Fourier-domain OCT” are known.
The configuration of a “time-domain OCT” is described, for example, in U.S. Pat. No. 5,321,501 with reference to FIG. 1a at column 5, line 40, to column 11, line 10. In a system of this kind, the optical path length of the reference beam path is continuously varied via a rapidly moving reference mirror. The light from specimen beam path and reference beam path is superposed on a photo detector. When the optical path lengths of the specimen and reference beam paths are coincident, an interference signal is provided on the photo detector.
A “Fourier-domain OCT” is, for example, described in international patent publication WO 2006/100544 A1. To measure the optical path length of a specimen beam path, light from the specimen beam path is superposed onto light from a reference beam path. In contrast to the time-domain OCT, the light from the specimen beam path and reference beam path is not supplied directly to a detector for a measurement of the optical path length of the specimen beam path but is first spectrally dispersed by means of a spectrometer. The spectral intensity of the superposed signal generated in this manner from specimen beam path and reference beam path is then detected by a detector. By evaluating the detector signal, the optical path length of the specimen beam path can be determined.